Tropical fossil forests unearthed in Arctic Norway

New
discovery could be the cause of a massive reduction in atmospheric CO2
levels hundreds of millions of years ago

UK researchers
have unearthed ancient fossil forests, thought to be partly responsible for one
of the most dramatic shifts in the Earth’s climate in the past 400 million
years.

The fossil
forests, with tree stumps preserved in place, were found in Svalbard, a
Norwegian archipelago situated in the Arctic Ocean. They were identified and
described by Dr Chris Berry of the School of Earth
and Ocean Sciences.

Prof John
Marshall, of Southampton University, has accurately dated the forests to 380
million years.

The forests
grew near the equator during the late Devonian period, and could provide an
insight into the cause of a 15-fold reduction in levels of carbon dioxide (CO2)
in the atmosphere around that time.

Current
theories suggest that during the Devonian period (420-360 million years ago)
there was a huge drop in the level of CO2 in the atmosphere, thought
to be largely caused by a change in vegetation from diminutive plants to the
first large forest trees.

Forests pulled
CO2 out of the air through photosynthesis – the process by which
plants create food and tissues – and the formation of soils.

Although
initially the appearance of large trees absorbed more of the sun’s radiation,
eventually temperatures on Earth also dropped dramatically to levels very
similar to those experienced today because of the reduction in atmospheric CO2.

Because of the
high temperatures and large amount of rainfall on the equator, it is likely
that equatorial forests contributed most to the drawdown of CO2.
Svalbard was located on the equator around this time, before the tectonic plate
drifted north by around 80° to its current position in the Arctic Ocean.

“These fossil
forests shows us what the vegetation and landscape were like on the equator 380
million years ago, as the first trees were beginning to appear on the Earth,”
said Dr Berry.

The team found
that the forests in Svalbard were formed mainly of lycopod trees, better known
for growing millions of years later in coal swamps that eventually turned into
coal deposits – such as those in South Wales. They also found that the forests
were extremely dense, with very small gaps – around 20cm – between each of the
trees, which probably reached about 4m high.

“During the
Devonian Period, it is widely believed that there was a huge drop in the level
of carbon dioxide in the atmosphere, from 15 times the present amount to
something approaching current levels.

“The evolution
of tree-sized vegetation is the most likely cause of this dramatic drop in
carbon dioxide because the plants were absorbing carbon dioxide through
photosynthesis to build their tissues, and also through the process of forming
soils.”